You can create your own sprocs for use by replication. Have a look at what the MS generated sprocs do (and in particular, the parameter) and then use that as the basis for your own, which you would code to lookup the extra values etc.

When you create the article(s) in the publication, just specify you custom sprocs and away you go. You will need to make sure that that exist - either create them directly or add them in a script that is run by replication when the subscription is established. I suspect that, since you have table definitions at your subscriber that are different from your published, it would probably easier for you to create the sprocs in advance.